Selecting the right state, event, or pulse data logger starts with understanding what each one measures and what question you are trying to answer. State loggers show whether equipment is on or off, event loggers record exactly when a change happens, and pulse loggers count signals from meters to measure usage, such as water or energy. This guide explains the difference, gives practical examples, and makes it easier to choose the right logger for your application.
A state data logger is a device that records whether a piece of equipment is on or off at regular, pre-set time intervals. It captures the operating condition of assets such as motors, pumps, compressors, lights, and HVAC units, making it the right choice when you need to measure run time, duty cycle, and overall utilisation rather than the exact moment of each switch.
Choose a state logger when the main question is how long the equipment ran or what percentage of time it was on. It is the best fit when you want straightforward time-based visibility rather than exact event sequencing.
An event data logger is a device that time-stamps every change of state the moment it happens. Instead of sampling at fixed intervals, it writes a new entry each time a contact opens or closes, producing a precise chronological log that is ideal for door-opening audits, alarm triggers, machine start/stop sequences, and compliance or security records.
Use an event logger when the exact timing of each change is critical. It is especially useful for fault diagnosis, alarm investigation, and audit trails.
A pulse data logger is a device that counts electrical pulses from a meter or sensor, where each pulse represents a fixed quantity of something measured. One pulse might equal a litre of water, a kilowatt-hour of electricity, or a cubic metre of gas, so these loggers are the standard tool for utility sub-metering, flow monitoring, and tenant billing applications.
Choose a pulse logger when the priority is measuring quantity, flow, consumption, or production output over time. It is the right option when the source device provides pulses rather than a simple on/off state.
Use this quick reference to match the logger type to the outcome you need.
| Logger type | What it records | Best for | Typical signals | Example use case |
|---|---|---|---|---|
| State | Current on/off status at set intervals | Duty cycle and run time percentage | Door switches, relay contacts, PLC outputs | See how long a pump runs each day |
| Event | Each change of state with exact time | Event timing, sequence tracking, and audits | Alarm relays, fault contacts, and access switches | Investigate when compressor faults occur |
| Pulse | Number of pulses over time, scaled to real units | Totals, usage rates, and consumption tracking | Flow meter pulses, energy meter outputs, counters | Track daily water or energy usage |
Select a logger by matching your signal type to your monitoring objective. State loggers show whether something is on or off over time, event loggers show exactly when changes happen, and pulse loggers measure quantity and usage.
If you already have a meter or instrument installed, its output type will usually narrow the correct logger choice quickly.
If the correct logger is still unclear, share the signal type, equipment details, and monitoring goal with your supplier before ordering.
Correct installation and setup are essential for reliable data.
Verify whether the logger expects a voltage-free contact, a voltage signal, or a defined pulse type from the connected device. For pulse logging, ensure the logger’s maximum input frequency matches the meter’s pulse rate to avoid missed counts.
Set state logging intervals to balance detail against memory usage. Use debounce or filtering on event and pulse inputs to reduce noise and false triggers. Apply the correct scaling factor so that reports display meaningful units such as litres, cubic metres, or kilowatt-hours.
State, event, and pulse loggers are complementary tools rather than competing products. When you consider runtime, timing, and consumption, selecting the appropriate logger is straightforward. The key is to match each logger to the correct signal, accurately configure intervals, debounce, and scaling, and validate the initial day of data before relying on subsequent results.
By mastering these fundamentals, a small set of well-selected loggers can provide insights that would otherwise require a costly, permanently installed monitoring system.
